Data from a Tesla Model S that crashed into a Utah fire truck on May 11 indicates the car accelerated for three to five seconds before the crash.

According to the Associated Press, the police suggested that a car traveling in front of the Tesla slowed down, causing the Autopilot-controlled Tesla to do the same. The leading car then changed lanes, prompting the Tesla to accelerate to regain its preset speed of 60 mph shortly before the crash.

The driver told the police that the Tesla had Autopilot engaged before the crash and that she had been looking at her phone. She suffered a broken ankle in the crash.

A Tesla Model S that crashed into a fire-department vehicle in South Jordan, Utah, while operating on Autopilot earlier this month accelerated for three to five seconds before the crash, according to data from the vehicle cited by the Associated Press on Thursday evening.

That is a new development amid the investigation of the May 11 crash, in which the driver of the Tesla suffered a broken ankle. The National Highway Traffic Safety Administration is investigating.

According to the AP’s report, the police suggested that the Tesla, which had been traveling at a preset speed of 60 mph, was behind another car that had slowed down to 55 mph. The Tesla slowed down as well, the report says, but when the leading car changed lanes, the Tesla accelerated to regain its speed shortly before impact.

The driver, whom the AP identified as Heather Lommatzsch, said she owned the Model S for two years and had used Autopilot on various types of roads. Lommatzsch reportedly told the police she believed the car’s automatic emergency-braking system would have detected traffic up ahead and stopped the vehicle before the crash.

Lommatzsch told the police her Model S was traveling with Autopilot activated and she had been looking at her phone at the time of the crash. Tesla recommends that drivers keep their hands on the steering wheel while using Autopilot and to be prepared to take full control of the vehicle at all times.

Tesla’s semiautonomous-driving technology emits multiple visual and audible warnings when it detects the driver’s hands are not on the steering wheel. The system will eventually deactivate itself if the driver ignores the warnings.

Vehicle data from the South Jordan crash indicated the driver’s hands were off the steering wheel for 80 seconds before the crash. It was not immediately clear whether Autopilot had deactivated.

Tesla has frequently reminded drivers to stay in control of their vehicles when using Autopilot. The system cannot cause Teslas to drive fully autonomously.

A Tesla representative did not immediately respond to Business Insider’s request for comment.